Use as an agent improving the workability of an aqueous formulation with a hydraulic binder base, of a (meth)acrylic comb-branched copolymer and an associative acrylic thickener

ABSTRACT

The present invention pertains to the use, in the manufacture of an aqueous formulation with a hydraulic binder base, of a combination of at least one comb-branched copolymer having a (meth)acrylic skeleton, onto which are grafted side-chains terminated by a hydrophilic group, and at least one ASE acrylic polymer. This results in improving the workability of said formulation, without causing a segregation phenomenon.

The present invention pertains to the field of admixtures which are usedin aqueous formulations with hydraulic binder bases, such as cements,concretes, or mortars, in order to improve their workability. Thehighest-performance among these workability agents today arecomb-branched polymers, which have a skeleton of a (meth)acrylic natureonto which are grafted monomers with hydrophilic functions, of thealcoxy- or hydroxy-polyakylene glycol type. These polymers are hereafterdesignated as “hydrophilic (meth)acrylic comb-branched polymers”.

However, until now their potential could not be optimally exploited: thedesire to overdose these admixtures has caused the formulation'smechanical properties to drop, and segregation, i.e. a physicalseparation between the various components of the mixture, has sometimesbeen observed.

The present invention, which, relies on combining these methacryliccomb-branched polymers having a grafted monomer with a hydrophilicfunction, with an ASE (alkali-soluble emulsion) associative acrylicthickener, makes it possible to advantageously remedy this drawback. Asa result, the workability of an aqueous formulation with a hydraulicbinder base is maintained over periods longer than three hours, withoutany segregation phenomenon nor loss of mechanical properties.

Reducing the quantity of water in formulations containing hydraulicbinders, though without altering their fluidity, is essential: thisresults in doping their mechanical properties. To do so, the personskilled in the art has for several years developed admixtures known as“water-reducing agents”, also known by the expressions “fluidifyingagents”, “plasticizers”. and “superplasticizers”. p Historically, thefirst of them were lignosulfonates, as described in the document U.S.Pat. No. 3,772,045, then polycondensates of formaldehyde and naphthaleneor melamine sulfonates were later used, as illustrated in the documentsU.S. Pat. No. 3,359,225 and U.S. Pat. No. 4,258,790.

Once adsorbed onto the surface of the cement particles, these polymers,which are negatively charged, cause a phenomenon of electrostaticrepulsion, which is the impetus for the cement particle dispersionmechanism; they require a dosage of about 0.4% solids content of thepolymer in relation to the solids content of the cement, as instructedin the document “Superplasticizers for extending workability”(International Conference on superplasticizers and other chemicaladmixtures in concrete, Sorrento Italy, Oct. 29-Nov. 1, 2006,supplementary paper, Ed. Malhotra, American Concrete Institute, pp.263-277)

A new better-performing family of water-reducing agents then appeared:that of carboxylic comb-branched polymers with a skeleton that isgenerally (meth)acrylic in nature, onto which are grafted hydrophilicside-chains with alcoxy- or hydroxy-polyalkylene glycol functions (seethe document cited above).

This improved water-reducing power is explained by the existence of asteric repulsion mechanism relating to the presence of the side-chains,in combination with the electrostatic repulsion phenomenon caused by theanionic carboxylic groups. This improvement leads to the ability to usea lower quantity of the polymer (on the order of 0.2% solids content inrelation to the cement's solids content) for a consistency comparable tothat obtained with the first-generation products.

However, in dosages like the ones described above, none of theseproducts of the prior art make it possible to resolve a criticaltechnical problem for the person skilled in the art: that of workabilityretention over very long periods, particularly longer than 3 hours.Workability is defined in document U.S. Pat. No. 7,232,875 as the timeduring which an aqueous formulation with a hydraulic binder base maystill be worked. This value is conventionally measured using a slumptest: the height is determined at which a sample added to a conical moldslumps when that mold is lifted. The greater the slump, the better theformulation's workability; if this nature is maintained over time, thisis called slump retention.

The person skilled in the art seeks to improve the lasting nature ofthis workability. Indeed, it is common to manufacture a cement orconcrete in a factory, in order to transport it later to the worksitewhere it is to be used; during this trip, which may take several hours,the formulation's workability must not be altered; otherwise, it can nolonger be worked. Alternatively, a new addition of water-reducing agentmust be available at the implementation site (this operation isimpossible if the formulation has begun to set), or a series ofinjections must be available during transport: The logistics andadditional cost that result are major drawbacks to using such solutions.

In order to maintain the workability of these formulations, the personskilled in the art has instinctively sought to “overdose” the quantityof water-reducing agents used, and particularly hydrophiliccomb-branched (meth)acrylic polymer water-reducing agents. Thisoverdosing is meant to extend the acting time of that agent. However, asis now well-known in this field of activity, this overdosing leads to aninitial fluidification which is too high.

Consequently, the fluidifying effect acts against the dispersionmechanism: the distribution of the components is no longer eventhroughout the formulation, which negatively impacts its mechanicalproperties. In some cases, the initial fluidifying power is sonoteworthy that it leads to segregation, i.e. a physical separation ofthe medium's various components. This issue is recounted in the documentWO 2007/047407.

Given the impossibility of overdosing the water-reducing agents of theprior art, and particularly hydrophilic comb-branched (meth)acrylicpolymers, the person skilled in the art has engineered alternativesolutions, so as to obtain a satisfactory initial fluidifying power andstable workability over time, without the undesirable effects ofsegregation or loss of mechanical properties.

Thus, the document WO 2007/047407 suggests the obvious solution ofadding a setting retarder agent, which raises problems of its own: theagent in and of itself constitutes a new admixture to add to theformulation, its dosage must be optimized based on the quantity ofwater-reducing agent used, and the resulting workability is no longerstable past two hours.

Other solutions consist of changes dealing with the composition of thehydrophilic comb-branched (meth)acrylic polymers of the prior art;however, they have the drawback of being focused on highly selectivechemical structures, and none of them lead to workability lasting longerthan three hours. Furthermore, they are all based on structural changes,intended to extend the fluidifying effect of the polymer that is usedover time. To that end, the document “Superplasticizers for extendingworkability” mentioned above, discloses the grafting of side-chains ofvarying lengths onto the main (meth)acrylic skeleton: they graduallyhydrolyze depending on their length, which maintains the dispersingeffect over time (up to two and a half hours according to FIG. 4).

At the same time, the document “Development of new superplasticizerproviding ultimate workability” (8th CANMET, Superplasticizers and otherchemical admixtures in concrete, 2008, Ed. Malhotra, American ConcreteInstitute, pp. 31-49) suggests increasing the number of hydrophilicbranches of a comb-branched (meth)acrylic polymer by adding adifunctional carboxylic comonomer onto the main skeleton: this resultsin a better adsorption of the polymer onto the surface of the cementparticles, and therefore stable workability for at least one and a halfhour according to table 5.

Finally, the document “development of slump-loss controlling agent withminimal setting retardation” (7th CANMET, Superplasticizers and otherchemical admixtures in concrete, 2003, Ed. Malhotra, American ConcreteInstitute, pp. 127-141) describes a comb-branched polymer whosehydrophilic side monomers have ester functions which hydrolyze moreslowly: this results in good workability for two and a half hours.

Continuing her research into providing an additive that would make itpossible to maintain a good level of initial fluidity in aqueousformulations with a hydraulic binder base, while maintaining theirworkability without altering their mechanical properties or causingsegregation phenomena to occur, the Applicant has developed the use ofnew admixtures resulting from the, mixing of a hydrophilic comb-branched(meth)acrylic copolymer in accordance with the prior art and ASEassociative acrylic thickeners.

ASE (alkali soluble emulsion) thickeners designate thickeners in anemulsion which are copolymers of (meth)acrylic acid with an ester ofthese acids. The Applicant indicates that such thickeners are differentfrom HASE (hydrophobically modified alkali-soluble emulsions) polymers,which designate thickeners in an emulsion which are copolymers of(meth)acrylic acid, an ester of these acids, and a hydrophobic monomer.

These chemicals' mechanisms of action differ. ASE polymers, in the formof dispersions when in an acidic state, only become soluble onceneutralized. By neutralizing the medium, an ionic repulsion mechanismsis caused between the various carboxylate groups carried by the polymerchain. These ionized groups polarize a large quantity of watermolecules, which causes the medium's viscosity to increase. In additionto the aforementioned ionic and polarizing phenomenon, HASE polymersinvolve interactions between the hydrophobic groups, which alsocontributes to thickening the medium. Entirely unexpectedly, when thesehydrophobic (meth)acrylic comb-branched copolymers are used in anaqueous formulation with a hydraulic binder base in the presence of ahydrophilic (meth)acrylic comb-branched copolymer, the result is a verylarge increase in the dose of the hydrophilic comb-branched copolymer inrelation to the prior art, without segregating or altering themechanical properties: quantities greater than 0.6% solids content ofhydrophilic comb-branched polymer in relation to the weight of thecement are achieved.

Doing so causes the formulation's workable time to be increased in amanner unlike any to date: values greater than three hours are achieved,as measured using a conventional slump test.

Therefore, a first object of the invention consists of the use, as anagent improving the workability of an aqueous formula with a hydraulicbinder base, of:

-   -   a) at least one comb-branched (meth)acrylic copolymer having at        least one side-chain bearing at least one alcoxy- or        hydroxy-polyalkylenc glycol hydrophilic group,    -   b) at least one ASE acrylic polymer.

In a first variant, this use as an agent improving the workability of anaqueous formula with a hydraulic binder base is further characterized inthat said comb-branched copolymer a) and said acrylic polymer b) areadded to said aqueous formulation separately.

In a second variant, this use as an agent improving the workability ofan aqueous formulation with a hydraulic binder base is furthercharacterized in that said comb-branched copolymer a) and said acrylicpolymer b) are added in the form of a mixture.

According to this variant, the mixture has a solids content between 10%and 50% of its total weight.

According to this variant, the mixture has a dry solids content ofcomb-branched copolymer a) of between 5% and 95%, and more preferablybetween 10% and 90% of its total solid matter.

This use is further characterized in that said comb-branched copolymera) is made up of, expressed as a percentage by weight of each of itsmonomers, the sum of these percentages being equal to 100%:

-   -   a1) 5% to 30% of (meth)acrylic acid,    -   a2) 70% to 95% of at least one monomer having the formula (I):

where:

-   -   -   m, n, p and q are whole numbers and m, n, p are less than            150, q is greater than 0, and at least one whole numbers            among m, n and p is nonzero;        -   R is a radical containing a polymerizable unsaturated            function, more preferably belonging to the group of vinylics            as well as the group of acrylic, methacrylic, and maleic            esters, and to the group of unsaturated urethanes such as            acrylurethane, methacrylurethane, α-α′            dimethyl-isopropenyl-benzylurethane, allylurethane, as well            as to the group of allylic or vinylic ethers, whether            substituted or not, or to the group of ethylenically            unsaturated amides or imides,        -   R₂ and R₂ are identical or different, and represent hydrogen            atoms or alkyl groups,        -   R′ represents hydrogen or a hydrocarbonated radical having 1            to 40 carbon atoms, or an ionic or ionizable group such as a            phosphate, a phosphonate, a sulfate, a sulfonate, a            carboxylic, or also a primary, secondary or tertiary amine,            or a quaternary ammonium, or mixtures thereof,

    -   a3) 0% to 50% of at least one monomer different from monomers        a1) and a2), and which is more preferably an ester, an amide, an        ether, a styrenic monomer, a cationic monomer, a sulfonated        monomer, a phosphated monomer, and which is very preferably        ethyl acrylate.

This use is also characterized in that said ASE acrylic polymers b) aremade up of (meth)acrylic acid and an ester of these acids.

This use is further characterized in that comb-branched copolymer a) andacrylic polymer b) may be obtained by radical polymerization in asolution, direct emulsion, or inverse emulsion, in a suspension orprecipitation in solvents, in the presence of catalytic systems andtransfer agents, or by radical mediated polymerization and morepreferably by nitroxide mediated polymerization (NMP) or cobaloxymemediated polymerization, by atom transfer radical polymerization (ATRP),or by radical mediated polymerization by sulfur derivatives, chosen fromamong carbamates, dithioesters or trithiocarbonatcs (RAFT) or xanthates.

This use is further characterized in that comb-branched copolymer a) andacrylic polymer b) are distilled, after polymerization.

This use is further characterized in that comb-branched copolymer a) andacrylic polymer b) are separated into several phases, using static ordynamic separation processes, by one or more polar solvents morepreferably belonging to the group formed by water, methanol, ethanol,propanol, isopropanol, butanols, acetone, tetrahydrofurane, and mixturesthereof.

This use is further characterized in that comb-branched copolymer a) andacrylic polymer b) are fully or partially neutralized by one or moreneutralization agents having a monovalent or polyvalent cation, saidagents more preferably being chosen from among ammonium hydroxide orfrom among calcium or magnesium hydroxides and/or oxides, or from amongsodium, potassium, or lithium hydroxides, or from among primary,secondary, and tertiary aliphatic and/or cyclic amines and morepreferably stearylamine, ethanolamines (mono-, di-, triethanolamine),mono- and diethylamine, cyclohexylamine, methylcyclohexylamine,amino-methyl-propanol, morpholine, and more preferably in that theneutralization agent is chosen from among triethanolamine and sodiumhydroxide.

This use as an agent improving the workability of an aqueous formulationwith a hydraulic binder base is further characterized in that saidformulation is a cement, a mortar, a concrete, or a grout, and morepreferably a concrete.

This use as an agent improving the workability of an aqueous formulationwith a hydraulic binder base of:

-   -   a) at least one comb-branched (meth)acrylic copolymer having al        least one side-chain bearing at least one alcoxy- or        hydroxy-polyalkylene glycol hydrophilic group,    -   b) at least one ASE acrylic polymer.

is further characterized in that said aqueous formulation with ahydraulic binder base contains 0.1% 2%, more preferably 0.2% to 1%, andvery preferably 0.4% to 0.8% solids content of components a) and b) inrelation to the solid content of hydraulic binder.

Another object of the invention consists of an aqueous formulation witha hydraulic binder base, containing as an agent improving itsworkability:

-   -   a) at least one comb-branched (meth)acrylic copolymer having at        least one side-chain bearing at least one alcoxy- or        hydroxy-polyalkylene glycol hydrophilic group,    -   b) at least one ASE acrylic polymer.

This formulation is further characterized in that said comb-branchedcopolymer a) is made up of, expressed as a percentage by weight of eachof its monomers, the sum of these percentages being equal to 100%:

-   -   a1) 5% to 30% of (meth)acrylic acid,    -   a2) 70% to 95% of at least one monomer having the formula (I):

where:

-   -   -   m, n, p and q are whole numbers and m, n, p are less than            150, q is greater than 0, and at least one whole numbers            among m, n and p is nonzero;        -   R is a radical containing a polymerizable unsaturated            function, more preferably belonging to the group of vinylics            as well as the group of acrylic, methacrylic, and maleic            esters, and to the group of unsaturated urethanes such as            acrylurethane, methacrylurethane, α-α′            dimethyl-isopropenyl-benzylurethane, allylurethane, as well            as to the group of allylic or vinylic ethers, whether            substituted or not, or to the group of ethylenically            unsaturated amides or imides,        -   R₁ and R2 are identical or different, and represent hydrogen            atoms or alkyl groups,        -   R′ represents hydrogen or a hydrocarbonated radical having 1            to 40 carbon atoms, or an ionic or ionizable group such as a            phosphate, a phosphonate, a sulfate, a sulfonate, a            carboxylic, or also a primary, secondary or tertiary amine,            or a quaternary ammonium, or mixtures thereof,

    -   a3) 0% to 50% of at least one monomer different from monomers        a1) and a2), and which is more preferably an ester, an amide, an        ether, a styrenic monomer, a cationic monomer, a sulfonated        monomer, a phosphated monomer, and which is very preferably        ethyl acrylate.

This formulation is further characterized in that said ASE acrylicpolymers b) are made up of (meth)acrylic acid and an ester of theseacids, and (meth)acrylic acid and an ester of these acids.

This formulation is further characterized in that comb-branchedcopolymer a) and acrylic polymer b) may be obtained by radicalpolymerization in a solution, direct emulsion, or inverse emulsion, in asuspension or precipitation in solvents, in the presence of catalyticsystems and transfer agents, or by radical mediated polymerization andmore preferably by nitroxide mediated polymerization (NMP) or bycobaloxyme mediated polymerization, by atom transfer radicalpolymerization (ATRP), by radical mediated polymerization by sulfurderivatives, chosen from among carbamates, dithioesters ortrithiocarbonates (RAFT) or xanthates.

This formulation is further characterized in that comb-branchedcopolymer a) and acrylic polymer b) are distilled, after polymerization.

This formulation is further characterized in that comb-branchedcopolymer a) and acrylic polymer b) are separated into several phases,using static or dynamic separation processes, by one or more polarsolvents more preferably belonging to the group formed by water,methanol, ethanol, propanol, isopropanol, butanols, acetone,tetrahydrofurane, and mixtures thereof.

This formulation is further characterized in that comb-branchedcopolymer a) and acrylic copolymer b) are fully or partially neutralizedby one or more neutralization agents having a monovalent or polyvalentcation, said agents being more preferably chosen from among ammoniumhydroxide or from among calcium or magnesium hydroxides and/or oxides,or from among sodium, potassium, or lithium hydroxides, or from amongprimary, secondary, and tertiary aliphatic and/or cyclic amines and morepreferably stearylamine, ethanolamines (mono-, di-, triethanolamine),mono- and diethylamine, cyclohexylamine, methylcyclohexylamine,amino-methyl-propanol, morpholine, and more preferably in that theneutralization agent is chosen from among triethanolamine and sodiumhydroxide.

This formulation is further characterized in that it is a cement, amortar, a concrete, or a grout, and more preferably a concrete.

This formulation is further characterized in that it contains 0.1% to2%, more preferably 0.2% to 1%, and very preferably 0.4% to 0.8% solidscontent of components a) and b) in relation to the solid content ofhydraulic binder.

EXAMPLES

In all tests, the molecular mass of the polymers used in aqueoussolutions a) are determined using a multi-detection steric exclusionchromatography (SEC 3D) technique, as indicated in the document FR2,917,091.

The masses of the polymers used in aqueous solutions b) are determinedusing a steric exclusion chromatography technique, as indicated in thedocument FR 2,907,347.

Example 1

The polymers used are obtained by polymerization techniques which arewell-known to the person skilled in the art.

All of the tests begin by adding into a masonry-style electric cementmixer (volume of about 100 liters) 22 kg of 10/20 aggregates and 25 kgof 0/4 sand, which are then mixed for 30 seconds.

Next, 6.5 kg of CEM 1 52.4 PM ES cement are added; this corresponds tothe starting time.

The dry materials are mixed for 1 minute.

Next, a certain quantity of an aqueous solution containing the productaccording to the prior art or according to the invention is added.

The mixing of the blend is then continued for 7 minutes.

The slump is then measured with an Abraham cone using the methoddescribed in the AFNOR EN 12350-2 standard. This first measurementcorresponds to the initial slump value, whose change is tracked overtime.

The slump of values has been depicted in FIG. 1, in centimeters of slumpover time in minutes.

The dotted curve with round symbols relates to Test 1 in accordance withthe prior art, in which it is necessary to add product to compensate forthe loss of workability (relative to the slump measurement).

The dotted curve with square symbols relates to Test 2 according to theprior art, in which the product is overdosed.

The solid curve with round symbols relates to Test 3 according to theinvention, which uses two products added separately.

The solid curve with square symbols relates to Test 4 according to theinvention, which uses two products added as a mixture.

Test No. 1

This test illustrates the prior art and uses 0.065 kg of an aqueoussolution (40% by weight) of a hydrophilic comb-branched copolymer, whosemolecular mass by weight is equal to 40,000 g/mol, made up of (byweight):

-   -   a1) 10% methacrylic acid,    -   a2) 90% of a monomer with formula (I) wherein:

m+n+p=56, q=1

-   -   -   R is the methacrylate function,        -   R₁ and R2 designate the methyl group,        -   R′ designates hydrogen

In this test, the product is (hydrophilic comb-branched polymer) used istherefore 0.40% solids content of the copolymer in relation to thecement's solids content, which corresponds to the dose normally used bythe person skilled in the art.

Tracking the change in slump over time (see the dashed curve with roundsymbols in FIG. 1), a reduction in slump is observed, meaning a verynoteworthy loss of workability.

At the end of 2 hours, it was sought to remedy this decrease by adding0.035 kg of the same aqueous solution containing the same copolymer: itsdose then became equal to 0.62% solids content of copolymer in relationto the cement's solids content.

Workability is then observed to rise again. However, it was necessary toadd the product: this represents both logistics which are complicated todevelop at an industrial scale, and an intermediate (and thereforeundesirable) change to the composition of the concrete.

Test No. 2

This test illustrates the prior art and uses 0.1 kg of the same aqueoussolution as the one used during Test 1.

In this situation, all of said solution is added at the beginning of thetest. The dose of the product (a hydrophilic comb-branched polymer) thatis used is equal to 0.62% by solids content in relation to the solidscontent of the cement: this illustrates an “overdosage” test assometimes practiced in the prior art.

First, it is noted that workability is less than that obtained with theinventive products (see FIG. 1).

Second, as shown in FIG. 2, which is a photo representing thecomposition at the initial moment, once the Abraham cone has beenremoved, a very noteworthy segregation phenomenon appears, which isundesirable for the person skilled in the art.

Test No. 3

This test illustrates the invention and uses 0.120 kg in total,including:

a) 90% by weight of the same aqueous solution as the one used in test 1,

b) 10% by weight of an aqueous solution of an ASE acrylic polymer (35%by weight), whose molecular mass by weight is equal to 40,000 g/mol andis made up, by weight, of:

-   -   b1) 55% methacrylic acid,    -   b2) 45% ethyl acrylate.        these two solutions a) and b) being added initially, but        separately.

In this test, 0.66% by solids content of hydrophilic comb-branchedcopolymer a) in relation to the cement's solids content is thereforeused.

Test No. 4

This test illustrates the invention and uses 0.120 kg of an aqueoussolution, containing:

a) 90% by weight of aqueous solution a) used in test 1,

b) 10% by weight of aqueous solution b) used in test 3.

The aqueous solution is initially added in the form of the mixturebetween solutions a) and b).

In this test, 0.66% by solids content of hydrophilic comb-branchedcopolymer a) in relation to the cement's solids content is thereforeused.

Tests 3 and 4 do not lead to any segregation phenomenon: however, theymake it possible to overdose the quantity of hydrophilic comb-branchedcopolymer a) that is used.

Additionally, and entirely advantageously, the result is a workabilitythat is at all points greater than that obtained for the prior art,without adding product later on.

Finally, this workability is entirely stable for 3 hours, which wasnever possible before.

Example 2

In all the following tests, a concrete is produced in the same way as inexample 1.

The slump is then measured with an Abraham cone using the methoddescribed in the AFNOR EN 12350-2 standard. This first measurementcorresponds to the initial slump value A₀ (cm). The same measurement istaken after 180 minutes A₁₈₀ (cm).

At the start, the concrete is checked to verify there is no segregation,and then the change in the slump value is checked after 180 minutes.

The following tests use a mixture of 2 aqueous solutions a) and b), themixture being initially introduced as in example 1.

Test No. 5

This test illustrates the invention and uses 0.360 kg of an aqueoussolution, containing:

a) 90% by weight of an aqueous solution (40% by weight) of a hydrophiliccomb-branched copolymer, whose molecular mass is equal to 45,000 g/moland is made up of (by weight):

-   -   a1) 10% methacrylic acid,    -   a2) 90% of a monomer with formula (I) wherein:

m+n+p=56, q=1

-   -   -   R is the methacrylate function,        -   R₁ and R2 designate the methyl group,        -   R′ designates hydrogen,

b) 10% by weight of aqueous solution b) used in test 3,

or alternatively 2.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

Test No. 6

This test illustrates the invention and uses 0.360 kg of an aqueoussolution, containing:

a) 90% by weight of an aqueous solution (40% by weight) of a hydrophiliccomb-branched copolymer, whose molecular mass is equal to 130,000 g/moland is made up of (by weight):

-   -   a1) 10% methacrylic acid,        -   a2) 90% of a monomer with formula (I) wherein:

+n+p=56, q=1

-   -   -   R is the methacrylate function,        -   R₁ and R₂ designate the methyl group,        -   R′ designates hydrogen,

b) 10% by weight of aqueous solution b) used in test 3,

or alternatively 2.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

Test No. 7

This test illustrates the invention and uses 0.360 kg of an aqueoussolution, containing:

a) 90% by weight of an aqueous solution (40% by weight) of a hydrophiliccomb-branched copolymer, whose molecular mass is equal to 74,000 g/moland is made up of (by weight):

-   -   a1) 10% methacrylic acid,    -   a2) 90% of a monomer with formula (I) wherein:

m+n+p=56, q=1

-   -   -   R is the methacrylate function,        -   R₁ and R2 designate the methyl group,        -   R′ designates hydrogen,

b) 10% by weight of aqueous solution b) used in test 3,

or alternatively 2.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

Test No. 8

This test illustrates the invention and uses 0.2025 kg of an aqueoussolution, containing:

a) 80% by weight of aqueous solution a) used in test 3,

b) 20% by weight of aqueous solution b) used in test 3,

or alternatively 1.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

Test No. 9

This test illustrates the invention and uses 0.180 kg of an aqueoussolution, containing:

a) 90% by weight of aqueous solution a) used in test 5,

b) 10% by weight of an aqueous solution of an ASE acrylic polymer (35%by weight), made up, by weight, of:

-   -   b1) 50% methacrylic acid,    -   b2) 50% ethyl acrylate.

or alternatively 1.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

Test No. 10

This test illustrates the invention and uses 0.240 kg of an aqueoussolution, containing:

a) 90% by weight of aqueous solution a) used in test 5,

b) 10% by weight of an aqueous solution of an ASE acrylic polymer, madeup, by weight, of:

-   -   b1) 50% methacrylic acid,        -   b2) 50% ethyl acrylate.

or alternatively 1.0% by weight of hydrophilic comb-branched copolymera) in relation to the solids content of cement.

None of these new tests led to a segregation phenomenon.

The slump values at the start A₀ (cm) and after 3 hours A₁₈₀ (cm) wererecorded in table 1, for test 2 which illustrates the prior art and fortests 3 to 10 which illustrate the invention.

TABLE 1 Prior Art (PA) Test no. Invention (IN) A₀ (cm) A₁₈₀ (cm) 2 PA 2218 3 IN 24 19.5 4 IN 24 18.5 5 IN 25 20 6 IN 25 21 7 IN 24 20 8 IN 23 199 IN 25 20 10 IN 23 20

Advantageously compared to the prior art, the invention successfullyincreases the dose of aqueous solution a).

The result in a substantial improvement in the initial workability withno phenomenon of segregation as in test 2.

This workability remains improved, even after 3 hours, which had neverbeen observed before.

1. A method for improving workability of an aqueous formulation with ahydraulic binder base, the method comprising: adding to the aqueousformulation, an agent comprising: a) at least one comb-branched(meth)acrylic copolymer having at least one side-chain bearing at leastone alcoxy- or hydroxy-polyalkylene glycol hydrophilic group; and b) atleast one ASE acrylic polymer.
 2. The method of claim 1, wherein thecomb-branched copolymer a) and the acrylic copolymer b) are addedseparately into the aqueous formulation.
 3. The method of claim 1,wherein the comb-branched copolymer a) and the acrylic copolymer b) areadded in the form of a mixture.
 4. The method of claim 3, wherein themixture has a dry solids content of between 10% and 50% of its totalweight.
 5. The method of claim 3, wherein the mixture has a dry solidscontent of comb-branched copolymer a) of between 5% and 95% of its totalsolid matter.
 6. The method of claim 1, wherein the comb-branchedcopolymer a) comprises expressed as a percentage by weight of each ofits monomers: a1) 5% to 30% of (meth)acrylic acid, a2) 70% to 95% of atleast one monomer having the of formula (I):

wherein: m, n, p, and q are whole numbers and m, n, and p are less than150, q is greater than 0, and at least one whole numbers among m, n, andp is nonzero; R is a radical comprising a polymerizable unsaturatedfunction; R₁ and R₂ are identical or different, and represent a hydrogenatom or an alkyl group. R′ represents hydrogen, or a hydrocarbonatedradical having 1 to 40 carbon atoms, or an ionic or ionizable group; a3)0% to 50% of at least one monomer different from monomers a1) and a2),wherein a sum of percentages equals 100%.
 7. The method of claim 1,wherein the ASE acrylic polymer b) comprises (meth)acrylic acid and anester of at least (meth)acrylic acid.
 8. The method of claim 1, whereinthe comb-branched copolymer a) and the ASE acrylic polymer b) areobtained by radical polymerization in a solution, direct emulsion, orinverse emulsion, in a suspension or precipitation in a solvent, in thepresence of at least one of a catalytic system and a transfer agent, byradical mediated polymerization, by cobaloxyme mediated polymerization,by atom transfer radical polymerization (ATRP), by radical mediatedpolymerization by at least one sulfur derivative selected from the groupconsisting of a carbamate, a dithioester, a trithiocarbonate, and axanthate.
 9. The method of claim 1, wherein the comb-branched copolymera) and acrylic polymer b) have been distilled, after polymerization. 10.The method of claim 1, wherein the comb-branched copolymer a) andacrylic polymer b) have been separated into several phases, by at leastone static or dynamic separation process, by at least one polar solventssolvent.
 11. The method of claim 1, wherein the comb-branched copolymera) and acrylic polymer b) are fully or partially neutralized by at leastone neutralization agent having a monovalent or polyvalent cation. 12.The method of claim 1, wherein the formulation is a cement, a mortar, aconcrete, or a grout.
 13. The method of claim 1, wherein the aqueousformulation with a hydraulic binder base comprises 0.1 % 2% solidscontent of components a) and b) in relation to a solid content ofhydraulic binder.
 14. An aqueous formulation, comprising: a hydraulicbinder base; and an agent comprising: a) at least one comb-branched(meth)acrylic copolymer having at least one side-chain bearing at leastone alcoxy- or hydroxy-polyalkylene glycol hydrophilic group; and b) atleast one ASE acrylic polymer.
 15. An aqueous formulation of claim 14,wherein the comb-branched copolymer a) comprises, expressed as apercentage by weight of each of its monomers: a1) 5% to 30% of(meth)acrylic acid, a2) 70% to 95% of at least one monomer having the offormula (I):

wherein: m, n, p, and q are whole numbers and m, n, and p are less than150, q is greater than 0, and at least one whole numbers among m, n, andp is nonzero; R is a radical comprising a polymerizable unsaturatedfunction, R₁ and R₂ are identical or different, and represent a hydrogenatom or an alkyl group, R′ represents hydrogen or a hydrocarbonatedradical having 1 to 40 carbon atoms, or an ionic or ionizable group, a3)0% to 50% of at least one monomer different from monomers a1) and a2),wherein a sum of percentages equals 100%.
 16. The aqueous formulation ofclaim 14, wherein the ASE acrylic polymer b) comprises (meth)acrylicacid and an ester of a (meth)acrylic acid.
 17. The aqueous formulationof claim 14, wherein the comb-branched copolymer -a) and acrylic polymerb) are obtained by radical polymerization in a solution, directemulsion, or inverse emulsion, in a suspension or precipitation insolvents, in the presence of catalytic at least one of a system and atransfer agent, by radical mediated polymerization, by cobaloxymemediated polymerization, by atom transfer radical polymerization (ATRP),by radical mediated polymerization by at least one sulfur derivativeselected from the group consisting of a carbamate, a dithioester, atrithiocarbonate, and a xanthate.
 18. The aqueous formulation of claim14, wherein the comb-branched copolymer a) and acrylic polymer b) havebeen distilled, after polymerization.
 19. The aqueous formulation ofclaim 14, wherein the comb-branched copolymer a) and acrylic polymer b)have been separated into several phases, be at least one static ordynamic separation process, by at least one polar solvent.
 20. Theaqueous formulation of claim 14, wherein the comb-branched copolymer a)and acrylic polymer b) are fully or partially neutralized by at leastone neutralization agent having a monovalent or polyvalent cation. 21.The aqueous formulation of claim 14, wherein the formulation is acement, a mortar, a concrete, or a grout.
 22. An aqueous formulation ofclaim 14, comprising 0.1% to 2%, solids content of components a) and b)in relation to a solid content of the hydraulic binder.